Sealing assembly

ABSTRACT

A sealing assembly ( 10 ) for sealing flexible packaging materials comprising: a sealing mechanism for sealing the packaging material; and a spreading mechanism for spreading the packaging material to be sealed prior to sealing, the spreading mechanism including at least two pair of opposed spreading members ( 15   a,    15   b ), each pair having opposing converging contact edges ( 17   a,    17   b ) which engage either side of the packaging material during spreading; wherein the spreading members are mounted for relative movement between a first open orientation and a second closed orientation such that, as the spreading members travel from said first to said second orientation, the contact edges initially contact the packaging material at convergent ends of the contact edges and then proceed to contact the packaging material along the length of the contact edges to divergent ends thereof, and wherein subsequently or simultaneously the spreading members engage the packaging material between the contact edges and travel transversely relative to the packaging material to spread the packaging material.

[0001] The present invention relates to a sealing assembly for sealingflexible packaging materials. In particular, the invention relates to asealing assembly which includes a spreading mechanism whichadvantageously facilitates spreading of the packaging material prior tosealing to alleviate problems associated with sealing through creases orother inconsistencies in the packaging film.

[0002] The sealing of flexible packaging materials is known and isgenerally employed in the production of, for example, bags. The basis ofmost packaging operations relies on sealing a flexible packagingmaterial around a product. In the case of packaging using a flexiblematerial, up to four seals may have to be made in the material to ensurethat the product is contained in the package. In the sealing process,the two faces of the packaging material must be brought together andbonded. This bonding or sealing process may take many forms. Forexample, the two faces may be bonded or sealed together using heat orcohesive or adhesive bonding.

[0003] In a large proportion of packaging applications with flexiblepackaging materials, it is a requirement that the seal or bond betweenthe two layers of material be hermetic. This hermetic bond or sealadvantageously prevents interaction of the packaged article with theoutside environment. This may be very important, for example, in thepackaging of products such as food products.

[0004] The process of creating a hermetic or high integrity seal canrely on several factors including:

[0005] (i) The sealability of the materials being bonded to each other.That is, the ability of the flexible packaging material to bond toitself or any other material being used.

[0006] (ii) The mechanism used to join the materials together. Forexample, in a thermal pressure or heat sealing system, this wouldinclude temperature, time and pressure. An adhesive system of sealingmay be determined on pressure and time.

[0007] (iii) The contact faces of the packaging material being free fromcreases or any other inconsistency. The removal of creases orinconsistencies allows the contact faces to be in intimate contactpromoting even pressure during bonding or sealing.

[0008] The sealing assembly of the invention is concerned with the finalfactor described above and advantageously provides an intimate contactbetween the contact faces of the packaging material without creases orinconsistencies prior to sealing of the packaging material.

[0009] According to the present invention there is provided a sealingassembly for sealing flexible packaging materials comprising:

[0010] a sealing mechanism for sealing the packaging material; and

[0011] a spreading mechanism for spreading the packaging material to besealed prior to sealing, the spreading mechanism including at least twopair of opposed spreading members, each pair having opposing convergingcontact edges which engage either side of the packaging material duringspreading;

[0012] wherein the spreading members are mounted for relative movementbetween a first open orientation and a second closed orientation suchthat, as the spreading members travel from said first to said secondorientation, the contact edges initially contact the packaging materialat convergent ends of the contact edges and then proceed to contact thepackaging material along the length of the contact edges to divergentends thereof, and wherein subsequently or simultaneously the spreadingmembers engage the packaging material between the contact edges andtravel transversely relative to the packaging material to spread thepackaging material.

[0013] In its simplest form, the sealing assembly according to theinvention includes two pair of opposed spreading members which, ineffect, act as jaw clamps, but which also act, due to their mounting, toinitially contact the packaging material and either while closing orsubsequent to closing on the packaging material, spread the packagingmaterial to remove creases and inconsistencies. Following this action,the sealing mechanism engages the packaging material between thespreading members and seals or bonds the packaging X material. In apreferred embodiment the two pair of spreading members are mountedsubstantially symmetrically about a substantially central longitudinalaxis of the packaging material. In this case, each of the pairs ofspreading members preferably initially contacts the packaging materialat or close to the central longitudinal axis of the packaging material.That is, the convergent ends of the spreading members are located at ornear the central longitudinal axis. Following the initial contact, thespreading members are disposed and mounted such that, as they movetogether toward the second orientation, the length of the contact edgesof the spreading members engage the packaging material untilsubstantially the entire length of the contact edges are in contact withthe packaging material. As will be illustrated in the accompanyingdrawings, this provides a symmetrical engagement of the packagingmaterial from the central point and then transversely across thepackaging material to each outer edge of the material.

[0014] If the sealing assembly includes only two pair of spreadingmembers, then the sealing mechanism is most preferably positionedimmediately next to the spreading members and in parallel alignment withthe spreading members. This arrangement is preferred as if the sealingmechanism is located at any substantial distance away from the spreadingmembers, then it may be possible that creases or inconsistencies willre-occur in the packaging material prior to reaching the sealingmechanism even though the spreading mechanism has acted to remove theseinconsistencies.

[0015] In an alternate and preferred embodiment, the spreading mechanismincludes four pairs of opposed spreading members, two of the pairs beingmounted parallel to each other and constituting a first side of thespreading mechanism and the other two of said pairs being mountedparallel to each other and constituting a second side of the spreadingmechanism, wherein the first and second sides of the spreading mechanismare symmetrical. This arrangement is, in a practical sense, equivalentto two parallel aligned mechanisms, each including the arrangementdescribed above in relation to the simplest form of the invention.

[0016] As was the case with the embodiment of the invention includingtwo pair of spreading members, it is preferred that the spreadingmembers of the first and second sides, equating to left and right sides,of the spreading mechanism are mounted such that convergent ends of thecontact edges of each pair of spreading members are located at asubstantially central longitudinal axis of the packaging material.Again, this arrangement facilitates spreading of the packaging materialacross its width from an initial central longitudinal axis of thematerial to either edge.

[0017] The sealing mechanism may include any suitable mechanism used inthe art. The sealing mechanism may be separate to or integral with thespreading mechanism. For example, in one embodiment the sealingmechanism includes at least one sealing bar which is separate to thespreading mechanism. However, in a preferred embodiment, the sealingmechanism includes a pair of sealing bars, each of the spreading membersbeing mounted on a respective one of the sealing bars such that sealingribbons which extend along the sealing bars are located between upperand lower pairs of the two pairs of spreading members which constitutethe first side of the spreading mechanism and upper and lower pairs ofthe two pairs of spreading members which constitute the second side ofthe spreading mechanism. In this sense, the spreading mechanism as awhole, if considered in the longitudinal direction of the packagingmaterial, includes a first set of spreading members comprising twoopposed pair of spreading members, two sealing bars each of whichincludes a sealing ribbon which extends transversely across thepackaging material, and finally a second set of spreading memberscomprising two pair of spreading members which are identical to thefirst set of spreading members. The upper four spreading members areadvantageously mounted relative to an upper one of the sealing bars,while the lower four spreading members are mounted relative to a lowerone of the sealing bars.

[0018] As has already been mentioned, the movement of the spreadingmembers between the first open orientation and the second closedorientation provides for the initial contact of the spreading memberswith the packaging material at convergent ends of the spreading members,and the subsequent spreading movement of the spreading members. In apreferred embodiment, each of the spreading members includes a spreadingplate having two slot and pin guides for guiding movement of thespreading plates between the first and second orientations. Morepreferably, the guides include a first inner guide located at theconvergent end of each spreading plate and a second outer guide locatedat the divergent end of each spreading plate. To facilitate initialmovement of the spreading members toward the packaging material andsubsequent movement of the spreading members in a transverse directionrelative to the longitudinal axis of the packaging material, the firstguide preferably includes a substantially L-shaped slot having a firstportion which extends from an outer edge of the support plate towardsthe contact edge of the support plate and a second portion which extendsat an angle from the first portion to facilitate transverse movement ofthe spreading plate to the second orientation, and the second guidepreferably includes a slot which extends from the outer edge of thespreading plate towards the contact edge of the spreading plate andwhich is substantially parallel to the second portion of the firstguide.

[0019] The pressure exerted by the spreading members on the packagingmaterial while travelling from the first to the second orientation, andin particular when travelling transversely to the longitudinal axis ofthe packaging material while spreading the packaging material, should besufficient to facilitate spreading of the packaging material, but shouldnot be so great as to cause grabbing of the packaging material or anystretching of the packaging material. In this sense, it is preferredthat the contact edges of the spreading members include a surface ofrigid short fibre brush.

[0020] In order to provide desired tensioning to the spreading members,in a preferred embodiment the upper and lower pairs of the two pairs ofspreading members which constitute the first side of the spreadingmechanism and the upper and lower pairs of the two pairs of spreadingmembers which constitute the second side of the spreading mechanism,each include a tensioning device for controlling tension between eachupper pair and lower pair of spreading members during movement of thespreading members between the first and second orientations. In aparticularly preferred embodiment, the tensioning device includes aspring.

[0021] The contact edges of each pair of spreading members may convergeat any suitable angle so as to ensure that the convergent ends of thecontact edges initially contact the packaging material, followed by theremainder of the contact edges. In a preferred embodiment, the spreadingmembers are disposed such that they rotate inwardly relative to thesubstantially central longitudinal axis of the packaging materialbetween the first and second orientations of the spreading members.Preferably, the angle of rotation of each of the spreading membersbetween the first and second orientation is from about 5° to about 45°.However, particularly good results have been found where the angle ofrotation of each of the spreading members between the first and secondorientation is from about 15° to about 20°.

[0022] A more detailed description of preferred embodiments of thesealing assembly according to the invention will now be described withreference to the accompanying drawings in which:

[0023]FIG. 1 illustrates a side elevational view of an upper half of asealing assembly including an upper pair of spreading members;

[0024]FIG. 2 illustrates an end elevation of the upper portion of FIG.1;

[0025]FIG. 3 illustrates the upper portion of FIG. 1 between its firstorientation and an intermediate orientation as it travels to its secondorientation;

[0026]FIG. 4 illustrates a complete sealing assembly with its spreadingmembers travelling from the first orientation to the second orientationwith packaging material therebetween; and

[0027]FIG. 5 illustrates a packing system which incorporates the sealingassembly.

[0028] Referring to FIGS. 1-4, the sealing assembly 10 includes an upperportion 11 and a lower portion 12 which include upper and lower sealingbars 13, 14 respectively. Spreading plates 15 a, 15 b are mounted on theupper and lower sealing bars 13, 14 and constitute a first pair ofspreading plates 15 a and a second pair of spreading plates 15 b. Thespreading plates 15 a, 15 b may also be described in terms of an “upperpair” which includes those mounted on sealing bar 13 and a “lower pair”which refers to those mounted on the lower sealing bar 14. Any referenceherein to “upper” and “lower” pairs of spreading plates should beunderstood to have this meaning. Furthermore, as can be readilyappreciated from FIG. 2, the sealing assembly 10 includes a second setof spreading plates 16 a, 16 b which are located on the opposite side ofsealing bars 13, 14 to the side on which spreading plates 15 a, 15 b aremounted. These spreading plates 16 a, 16 b act in a symmetrical fashionto spreading plates 15 a, 15 b and, as such, reference to movement ofspreading plates 15 a, 15 b should also be considered to be referencedto movement to the second set of spreading plates 16 a, 16 b. Thesespreading plates 16 a, 16 b are best illustrated in FIG. 5.

[0029] Spreading plates 15 a and 15 b are mounted on upper and lowersealing bars 13, 14 such that contact edges 17 a, 17 b of the spreadingplates are disposed at an angle and converge towards a centrallongitudinal axis of the packaging material 20. Convergent ends 18 a, 18b, due to the convergence of the contact edges 17 a, 17 b, are the firstpoints to contact the packaging material 20 as the sealing bars 13, 14move towards each other.

[0030] Movement of the spreading plates 15 a, 15 b is controlled byguides 21 and 22. Each of the spreading plates includes the guides 21,22. As such, these guides will be now described singularly, but itshould be understood that this description applies to each of thespreading plates of the sealing assembly.

[0031] The first guide 21 is substantially L-shaped and includes a firstportion 21 a and a second portion 21 b. The first portion 21 a extendsfrom an outer edge of the spreading plate 15 a towards the contact edge17 a of the spreading plate. The second portion 21 b of guide 21 extendsat an angle from the first portion 21 a toward the convergent end 18 aof the spreading plate 15 a. The second guide 22 is smaller than thefirst guide 21 and is located more toward the divergent end 19 a of thespreading plate 15 a. The second guide 22 again extends from the outeredge of the spreading plate 15 a, although the second guide is insetfrom the outer edge, towards the contact edge 17 a. Further, the secondguide 22 is substantially parallel to the second portion 21 b of thefirst guide 21. Each of the guides 21, 22 includes a slot and pinarrangement. Advantageously, the pin includes a bearing arrangement tofacilitate substantially frictionless movement of the pin through theslot.

[0032] Referring to FIG. 4, the travel of the assembly 10 from the firstorientation through to the second orientation is depicted. In the firstorientation, as illustrated in FIG. 4.1, the spreading plates 15 a, 15 bare spaced apart with the packaging material 20 located therebetween inan expanded form. That is, gas flow is used to produce a positivepressure in the packing material tube relative to the surrounding areaso as to partially inflate the tube. As the spreading plates 15 a, 15 bmove towards each other, convergent ends 18 a, 18 b of the spreadingplates initially contact the packaging material 20 at a substantiallycentral longitudinal axis of the packaging material. This forces thepackaging material tube to be substantially collapsed as illustrated inFIG. 4.2, wherein gas within the tubing is forced to outer edges of thetubing. At this point, pins 23 in the first guide 21 are travellingwithin the slot of the first portion 21 a. As the pins 23 move throughslot 21 a of the first guide 21, the contact edges 17 a, 17 b of thespreading plates 15 a, 15 b engage the packaging material to itstransverse edges until the spreading plates 15 a, 15 b reach anintermediate orientation as depicted in FIG. 4.3. At this point, thepins 23 are located at the juncture of the first portion 21 a and thesecond portion 21 b of the first guide 21. However, the pins 24 whichare located in slots of the second guides have not moved along thesecond guides. The angle of rotation of the spreading plates 15 a, 15 bbetween the first orientation and the intermediate orientation isadvantageously between 15° and 200.

[0033] In order to spread the packing material 20 which is now engagedby the length of the contact edges 17 a, 17 b, the spreading plates 15a, 15 b must travel in transverse directions relative to thelongitudinal axis of the packaging material 20. That is, the pair ofspreading plates 15 a travel toward one transverse edge of the packagingmaterial 20 while the other pair of spreading plates 15 b travel towardsan opposing edge of the packaging material. This movement is bestillustrated in FIG. 4.4 and results in the spreading plates 15 a, 15 breaching the second orientation depicted in FIG. 4.5. During movementbetween the intermediate orientation seen in FIG. 4.3 and the secondorientation seen in FIG. 4.5, pins 23, 24 travel in the slots of thesecond portion 21 b of the first guide 21 and the slots of the secondguide 22 respectively.

[0034] The spreading plates 15 a, 15 b are tensioned so that thepressure applied to the packaging material 20 when the spring plates aremoving from the intermediate orientation to the second orientation issufficient to remove creases and inconsistencies in the packagingmaterial 20, but is not so great so as to stretch the packaging materialor grab the packaging material. Preferably, a spring 25 is provided as atensionsing device between each upper and lower pair of plates 15 a, 15b so as to suitably control the pressure applied to the packagingmaterial 20 by the contact edges 17 a, 17 b of the spreading plates 15a, 15 b. Furthermore, to ensure that the packaging material 20 is notpinched by the convergent ends 18 a, 18 b of the spreading plates 15 a,15 b of the spreading plates 15 a, 15 b, the convergent ends arebevelled so that there is no gap between pairs of upper and lower platesprior to initial contact with the packaging material 20.

[0035] Referring to FIG. 5, a packaging system is illustrated whichincludes a feed of packaging film 51 which is fed to a forming frame 52.The packaging material is then inflated by means of a gas flow H from aninflation apparatus fan or gas exhaust port 53, the packaging materialthen passes through a fin or long seal apparatus 54 which forms thepackaging material into a tube.

[0036] Product is inserted into the packaging material at any suitabletime, generally before forming the packaging material into a tube.Product is fed by means of a main transport conveyor belt 55. Thesealing assembly 10 acts to seal the packing material at either end ofthe product as described hereabove. The final packaged product isconveyed by means of an outfeed conveyor 56.

[0037] Throughout this specification and the claims which follow, unlessthe context requires otherwise, the word “comprise”, and variations suchas “comprises” and “comprising”, will be understood to imply theinclusion of a stated integer or step or group of integers or steps butnot the exclusion of any other integer or step or group of integers orsteps.

[0038] The reference to any prior art in this specification is not, andshould not be taken as, an acknowledgment or any form of suggestion thatthat prior art forms part of the common general knowledge in Australia.

[0039] Those skilled in the art will appreciate that the inventiondescribed herein is susceptible to variations and modifications otherthan those specifically described. It is to be understood that theinvention includes all such variations and modifications which fallwithin its spirit and scope. The invention also includes all the steps,features, compositions and compounds referred to or indicated in thisspecification, individually or collectively, and any and allcombinations of any two or more of said steps or features.

1. A sealing assembly for sealing flexible packaging materialscomprising: a sealing mechanism for sealing the packaging material; anda spreading mechanism for spreading the packaging material to be sealedprior to sealing, the spreading mechanism including at least two pair ofopposed spreading members, each pair having opposing converging contactedges which engage either side of the packaging material duringspreading; wherein the spreading members are mounted for relativemovement between a first open orientation and a second closedorientation such that, as the spreading members travel from said firstto said second orientation, the contact edges initially contact thepackaging material at convergent ends of the contact edges and thenproceed to contact the packaging material along the length of thecontact edges to divergent ends thereof, and wherein subsequently orsimultaneously the spreading members engage the packaging materialbetween the contact edges and travel transversely relative to thepackaging material to spread the packaging material.
 2. A sealingassembly according to claim 1, wherein said two pair of spreadingmembers are mounted substantially symmetrically about a centrallongitudinal axis of the packaging material.
 3. A sealing assemblyaccording to claim 1, wherein said spreading mechanism includes fourpairs of opposed spreading members, two of said pairs being mountedparallel to each other and constituting a first side of said spreadingmechanism and the other two of said pairs being mounted parallel to eachother- and constituting a second side of said spreading mechanism,wherein said first and second sides of said spreading mechanism aresymmetrical.
 4. A sealing assembly according to claim 3, wherein thespreading members of said first and second sides of said spreadingmechanism are mounted such that convergent ends of the contact edges ofeach pair of spreading members are located at a substantially centrallongitudinal axis of said packaging material.
 5. A sealing assemblyaccording to claim 3, wherein the sealing mechanism includes at leastone sealing bar which is separate to said spreading mechanism.
 6. Asealing assembly according to claim 3, wherein the sealing mechanismincludes a pair of sealing bars, each of said spreading members beingmounted on a respective one of said sealing bars such that sealingribbons which extend along said sealing bars are located between upperand lower pairs of the two pairs of spreading members which constitutethe first side of the spreading mechanism and upper and lower pairs ofthe two pairs of spreading members which constitute the second side ofthe spreading mechanism.
 7. A sealing assembly according to claim 1,wherein each of said spreading members includes a spreading plate having2 slot and pin guides for guiding movement of the spreading platesbetween said first and second orientations.
 8. A sealing assemblyaccording to claim 7, wherein said guides include a first inner guidelocated at the convergent end of said spreading plate and an outer guidelocated at the divergent end of said spreading plate.
 9. A sealingassembly according to claim 8, wherein the first guide includes asubstantially L-shaped slot having a first portion which extends from anouter edge of the support plate towards the contact edge of the supportplate and a second portion which extends at an angle from the firstportion to facilitate transverse movement of the spreading plate to saidsecond orientation, and wherein the second guide includes a slot whichextends from the outer edge of the spreading plate towards the contactedge of the spreading plate and which is substantially parallel to thesecond portion of the first guide.
 10. A sealing assembly according toclaim 3, wherein upper and lower pairs of the two pairs of spreadingmembers which constitute the first side of the spreading mechanism andupper and lower pairs of the two pairs of spreading members whichconstitute the second side of the spreading mechanism each include atensioning device for controlling tension between each upper and lowerpair of the spreading members during movement of the spreading membersbetween the first and second orientations.
 11. A sealing assemblyaccording to claim 10, wherein said tensioning device is a spring.
 12. Asealing assembly according to claim 1, wherein the angle of rotation ofeach of said spreading members between said first and second orientationis from about 5° to about 45°.
 13. A sealing assembly according to claim12, wherein the angle of rotation of each of said spreading membersbetween said first and second orientation is from about 15° to about20°.